Built in 1903/04, this building was home to the First National Bank from 1904 to 1960. It was remodeled in 1922 to its present appearance, including the addition of a distinctive outdoor clock. It was the first home of the O'Fallon Public Library upstairs from 1930 to 1945 and its third home downstairs from 1962 to 1995. Upstairs also housed Smiley Bros. Telephone Exchange from 1904 to 1952, as well as various businesses, professionals, and city offices. It became the O'Fallon Historical Museum in 1996.